What is typically added to water with high hardness and alkalinity to raise pH?

The correct answer is the use of quicklime or hydrated lime to raise the pH in water with high hardness and alkalinity. When added to water, quicklime (calcium oxide) reacts with the water to form calcium hydroxide, which increases the pH level by making the water more alkaline. This is particularly useful in water treatment processes, where adjusting pH can improve the effectiveness of disinfection and help precipitate out certain minerals, thereby reducing hardness.

Quicklime is effective because it dissolves readily in water, providing a strong alkaline solution that can effectively neutralize any acidic components in the water, thus raising the pH. Hydrated lime, which is calcium hydroxide in its solid form, serves a similar purpose and is often easier to handle and transport than quicklime.

In contrast, soda ash (sodium carbonate), while it can raise pH, is less effective in areas where hardness is primarily due to calcium and magnesium ions. Humanitarian lime is not a standard term in water treatment and might refer to a variation of hydrated lime, though it's not commonly used in these contexts. Calcium sulfate acts as a source of calcium but does not significantly raise pH and can contribute to the hardness of water, making it not suitable for